Liquid crystal displays (LCDs) have been used for many years as display devices. Originally, LCD devices served as low-speed monochromatic displays for clocks, and status indicators for electronic devices. More recently, however, LCD devices have been used in full color displays for computers, navigation systems and televisions.
Some high quality LCD display devices, such as those used for computer monitors and television displays, include a backlit LCD pixel panel. The LCD pixel panel contains an array of red, green and blue pixels disposed over a light source. By electronically controlling the transparency of each pixel, an image is generated on the LCD pixel panel.
Conventionally, backlights have been constructed using light sources such as incandescent light bulbs, an electroluminescent panel (ELP), one or more cold cathode fluorescent lamps (CCFL), and hot cathode fluorescent lamps (HCFL). In some cases, a light diffuser is used to provide even illumination from uneven light sources. Most recently, however, arrays of light emitting diodes (LEDs) have been employed in back lights. Display devices using LED backlighting have made very thin flat panel displays possible due to the low power and compact size of the LEDs.
One limitation of many commercially available LCD display devices is the inability of pixels on the pixel panel to become completely opaque, thereby allowing light to leak through the display in regions where pixels are designated to be off. This effect, commonly known as “black light leakage,” reduces picture contrast and makes black areas of the picture appear grey in color.